Avicennia dominated mangrove forests occur from seaward to landward sites and hence are subject to different dynamics within estuarine ecosystems. Regeneration of mangrove forests primarily depends on the extent of propagule spread and subsequent establishment in suitable habitats. The complex nature of estuarine systems induces a wide variety of local conditions for within-site propagule retention and settlement thereby allowing spontaneous regeneration of mangroves. In this study, we estimated the fine-scale spatial genetic structure (FSGS) of Avicennia populations and examined whether their position relative to the seaside or the size of mangrove patches could have influenced the extant local population genetic structure. A kinship-based FSGS was performed using microsatellite markers in 523 A. marina, 189 A. rumphiana and 60 A. alba adult trees of 24 sites in The Philippines. Transects within each estuary were taken both parallel and perpendicular to the coastline or tidal river edge. The extent of local mangrove areas and various human-induced encroachments as such did not show any trend in allele diversity, heterozygosity values or inbreeding levels. However, farther inland situated mangrove patches showed a larger FSGS extent across the neighborhood (up to 75 m) though less diversity along with inbreeding, most likely due to retention of related propagules and lowered chance of external propagule input. Estimation of connectivity along a same coastline stretch supported a unidirectional steppingstone or adjacent migration model for populations of either A. marina, A. alba or A. rumphiana. These were congruent with ocean currents across mangrove estuaries of the Tablas Strait and along Western Leyte, thereby emphasizing the relevance of coastal connectivity for long term persistence. From this study, we conclude that both proximity to open water and narrowness of mangrove patches may affect their captured diversity, inbreeding and fine-scale structure caused by propagule movement within or beyond a local mangrove fragment during recent generations. Higher levels of allele diversity for seaward sites and highest likelihood of migration for adjacent mangroves both add to the importance of coastal connectivity that is the only natural cohesive force on longer term and necessary to counteract short term effects of increasingly encroached mangrove environments.

中文翻译：

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沿岸红树林碎片的邻近性影响Avicennia的遗传多样性和精细尺度的结构

以紫花苜蓿为主的红树林从海域到陆域都存在，因此在河口生态系统内受到不同动力的影响。红树林的更新主要取决于繁殖体的扩散程度以及随后在合适的栖息地中的建立。河口系统的复杂性质引发了多种多样的局部条件，用于现场繁殖体的滞留和沉降，从而允许红树林自发再生。在这项研究中，我们估计了Avicennia种群的精细尺度空间遗传结构（FSGS），并检查了它们相对于海边的位置或红树林斑块的大小是否可能影响了现有的当地种群遗传结构。使用微卫星标记在523 A. marina，189 A. rumphiana和60 A中使用基于亲属关系的FSGS。菲律宾24个地点的晨曲成年树木。每个河口内的横断面均平行于或垂直于海岸线或潮汐河沿。当地的红树林区域和各种人类诱发的侵袭的程度在等位基因多样性，杂合度值或近交水平方面均未显示任何趋势。然而，内陆较远的红树林斑块在整个邻里（最大75 m）显示出更大的FSGS范围，尽管随着近交繁殖的多样性降低，最有可能是由于保留了相关繁殖体和降低了外部繁殖体输入的机会。沿同一海岸线的连通性的估算支持了A. marina，A。alba或A. rumphiana种群的单向踏脚石或相邻的迁移模型。这些与塔布拉斯海峡的红树林河口和西部的莱特河上的洋流相吻合，从而强调了沿海连通性对长期持久性的重要性。从这项研究中，我们得出结论，由于近代世代在局部或非局部的红树林中传播繁殖所致，靠近开阔水域和红树林斑块的狭窄都可能影响其捕获的多样性，近交和精细规模的结构。沿海地点等位基因多样性的提高和相邻红树林迁移的可能性都增加了沿海连通性的重要性，沿海连通性是长期的唯一自然凝聚力，并且是应对日益侵蚀的红树林环境的短期影响所必需的。因此，强调了沿海连通性对长期持久性的重要性。从这项研究中，我们得出结论，由于近代世代在局部或非局部的红树林中传播繁殖所致，靠近开阔水域和红树林斑块的狭窄都可能影响其捕获的多样性，近交和精细规模的结构。沿海地点等位基因多样性的提高和相邻红树林迁移的可能性都增加了沿海连通性的重要性，沿海连通性是长期的唯一自然凝聚力，并且是应对日益侵蚀的红树林环境的短期影响所必需的。因此，强调了沿海连通性对长期持久性的重要性。从这项研究中，我们得出结论，由于近代世代在局部或非局部的红树林中传播繁殖所致，靠近开阔水域和红树林斑块的狭窄都可能影响其捕获的多样性，近交和精细规模的结构。沿海地点等位基因多样性的提高和相邻红树林迁移的可能性都增加了沿海连通性的重要性，沿海连通性是长期的唯一自然凝聚力，并且是应对日益侵蚀的红树林环境的短期影响所必需的。近代繁殖体在局部红树林内部或外部传播所引起的近交和小规模结构。沿海地点等位基因多样性的提高和相邻红树林迁移的可能性都增加了沿海连通性的重要性，沿海连通性是长期的唯一自然凝聚力，并且是应对日益侵蚀的红树林环境的短期影响所必需的。近代繁殖体在局部红树林内部或外部传播所引起的近交和小规模结构。沿海地点等位基因多样性的提高和相邻红树林迁移的可能性都增加了沿海连通性的重要性，沿海连通性是长期的唯一自然凝聚力，并且是应对日益侵蚀的红树林环境的短期影响所必需的。